// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_FILTERS_VPX_VIDEO_DECODER_H_
#define MEDIA_FILTERS_VPX_VIDEO_DECODER_H_

#include "base/callback.h"
#include "base/macros.h"
#include "base/threading/thread_checker.h"
#include "media/base/demuxer_stream.h"
#include "media/base/video_decoder.h"
#include "media/base/video_decoder_config.h"
#include "media/base/video_frame.h"
#include "media/base/video_frame_pool.h"

struct vpx_codec_ctx;
struct vpx_image;

namespace base {
class SingleThreadTaskRunner;
}

namespace media {

// Libvpx video decoder wrapper.
// Note: VpxVideoDecoder accepts only YV12A VP8 content or VP9 content. This is
// done to avoid usurping FFmpeg for all VP8 decoding, because the FFmpeg VP8
// decoder is faster than the libvpx VP8 decoder.
// Alpha channel, if any, is sent in the DecoderBuffer's side_data() as a frame
// on its own of which the Y channel is taken [1].
// [1] http://wiki.webmproject.org/alpha-channel
class MEDIA_EXPORT VpxVideoDecoder : public VideoDecoder {
public:
    VpxVideoDecoder();
    ~VpxVideoDecoder() override;

    // VideoDecoder implementation.
    std::string GetDisplayName() const override;
    void Initialize(const VideoDecoderConfig& config,
        bool low_delay,
        CdmContext* cdm_context,
        const InitCB& init_cb,
        const OutputCB& output_cb) override;
    void Decode(const scoped_refptr<DecoderBuffer>& buffer,
        const DecodeCB& decode_cb) override;
    void Reset(const base::Closure& closure) override;

private:
    enum DecoderState {
        kUninitialized,
        kNormal,
        kFlushCodec,
        kDecodeFinished,
        kError
    };

    // Return values for decoding alpha plane.
    enum AlphaDecodeStatus {
        kAlphaPlaneProcessed, // Alpha plane (if found) was decoded successfully.
        kNoAlphaPlaneData, // Alpha plane was found, but decoder did not return any
        // data.
        kAlphaPlaneError // Fatal error occured when trying to decode alpha plane.
    };

    // Handles (re-)initializing the decoder with a (new) config.
    // Returns true when initialization was successful.
    bool ConfigureDecoder(const VideoDecoderConfig& config);

    void CloseDecoder();

    // Helper method for decoding buffers either on the offload thread or directly
    // on the media thread. |bound_decode_cb| must be bound to the thread that
    // called Decode().
    void DecodeBuffer(const scoped_refptr<DecoderBuffer>& buffer,
        const DecodeCB& bound_decode_cb);

    // Try to decode |buffer| into |video_frame|. Return true if all decoding
    // succeeded. Note that decoding can succeed and still |video_frame| be
    // nullptr if there has been a partial decoding.
    bool VpxDecode(const scoped_refptr<DecoderBuffer>& buffer,
        scoped_refptr<VideoFrame>* video_frame);

    bool CopyVpxImageToVideoFrame(const struct vpx_image* vpx_image,
        const struct vpx_image* vpx_image_alpha,
        scoped_refptr<VideoFrame>* video_frame);

    AlphaDecodeStatus DecodeAlphaPlane(
        const struct vpx_image* vpx_image,
        const struct vpx_image** vpx_image_alpha,
        const scoped_refptr<DecoderBuffer>& buffer);

    base::ThreadChecker thread_checker_;

    // |state_| must only be read and written to on |offload_task_runner_| if it
    // is non-null and there are outstanding tasks on the offload thread.
    DecoderState state_;

    OutputCB output_cb_;

    VideoDecoderConfig config_;

    vpx_codec_ctx* vpx_codec_;
    vpx_codec_ctx* vpx_codec_alpha_;

    // |memory_pool_| is a single-threaded memory pool used for VP9 decoding
    // with no alpha. |frame_pool_| is used for all other cases.
    class MemoryPool;
    scoped_refptr<MemoryPool> memory_pool_;

    // High resolution vp9 may block the media thread for too long, in such cases
    // we share a per-process thread to avoid overly long blocks.
    scoped_refptr<base::SingleThreadTaskRunner> offload_task_runner_;

    VideoFramePool frame_pool_;

    DISALLOW_COPY_AND_ASSIGN(VpxVideoDecoder);
};

} // namespace media

#endif // MEDIA_FILTERS_VPX_VIDEO_DECODER_H_
